Create a 3d model with python API using Postgis Polygon
With help of @TLousky's answer and @batFINGER's comment, finally this worked for me.

import bpy, json, bmesh
from math import *
from mathutils import Vector


data_string = '{"type":"Polygon","coordinates":[[[-121.332737,38.722023],[-121.332895,38.722023],[-121.332895,38.721977],[-121.332946,38.721977],[-121.332946,38.721881],[-121.332737,38.721881],[-121.332737,38.722023]]]}'

dataDict = json.loads( data_string )



coordinates = dataDict['coordinates'][0]

x_factor = coordinates[0][0]
y_factor = coordinates[0][1]


verts = tuple([((x[0] - x_factor)*10000, (x[1] - y_factor)*10000) for x in coordinates])

bm = bmesh.new()



bm = bmesh.new()
for v in verts:
    bm.verts.new((v[0], v[1], 0))




# Generate one ngon face
bottom = bm.faces.new(bm.verts)

top = bmesh.ops.extrude_face_region(bm, geom=[bottom])


bmesh.ops.translate(bm, vec=Vector((0,0,1)), verts=[v for v in top["geom"] if isinstance(v,bmesh.types.BMVert)])

bm.normal_update()

# Generate a mesh and transfer data from bmesh object
m = bpy.data.meshes.new('GIS')


bm.to_mesh(m)



# Create a new mesh object and link to scene
o = bpy.data.objects.new('GIS', m)

bpy.context.scene.objects.link(o)